Automotive power supply

ABSTRACT

The automotive electric power supply includes a rechargeable battery and a distributor comprising an input for one battery terminal and several outputs furnishing the battery voltage for various consumers. Arranged between the input for one battery terminal and the outputs are semiconductor switches driven by a digital controller. The controller has an input interface for sensor signals representing operating parameters. The power supply is smart in ensuring that electrical energy is furnished to the various consumers in the vehicle only as required.

FIELD OF INVENTION

[0001] The present invention relates to an automotive electric powersupply.

BACKGROUND OF THE INVENTION

[0002] The electrical energy needed in vehicles for powering the variouselectrical consumers is taken from a rechargeable battery which ischarged by an alternator from operation of the internal combustionengine. One of the battery terminals is directly connected to vehicleground, the other battery terminal, generally the positive terminal, isfed to various consumers via a distributor including several outputs andintegrated fuses.

BRIEF SUMMARY OF THE INVENTION

[0003] The invention provides an automotive electric power supply whichis smart in optimizing the energy reserve made available by therechargeable battery according to the demands. In accordance with theinvention, between the input for one battery terminal and at least oneof the outputs of the distributor, a semiconductor switch is connectedwhich is driven by an electronic controller; the controller has an inputinterface for sensor signals representing operating parameters. Thecontroller is thus active in controlling the consumer(s) connected tothe output provided with a semiconductor switch. This control mayinvolve power ON/OFF as required or also modulation, more particularlypulse width modulation.

[0004] In one particularly advantageous embodiment of the invention atleast the one output connected to the vehicle lighting formedsubstantially by incandescent bulbs is regulated by pulse widthmodulation to a voltage value as defined effective for the incandescentbulbs. Now, the charging voltage supplied by the alternator for therechargeable battery no longer needs to be limited to a value, takinginto account the life of the incandescent bulbs, which is sigificantlylower than the optimum charging voltage under certain operatingconditions.

[0005] It is further provided for in the preferred embodiment togenerate a parameter representing the charge condition of therechargeable battery by permanently monitoring the charging/dischargingcurrents and integrating the current values as sensed. Depending on thecharge condition of the battery the various consumers can then besupplied from the rechargeable battery according to a priority scheme.This concept enables essential functions to be maintained over anextended time period when the battery is low so that the vehicle canremain operative longer, for example, when the alternator is down.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Further features and advantages of the invention read from thefollowing description and are evident from the drawings to whichreference is made and in which

[0007]FIG. 1 is a block diagram of the electric power supply;

[0008]FIG. 2 is a schematic illustration of a means for current sensingby means of magnetoresistive elements,

[0009]FIG. 3 is a graph plotting starter current with time for variousoperating conditions;

[0010]FIG. 4 is a graph plotting the charging condition; and

[0011]FIG. 5 is a graph plotting the current furnished by the alternatorafter rectification.

DETAILED DESCRIPTION OF THE INVENTION

[0012] Referring now to FIG. 1 there is illustrated a power supplyincorporated in a housing 10 mounted on the rechargeable battery 12,preferably directly next to the positive terminal. The power supply hasan input 14 directly connected to the positive terminal of the battery.Furthermore, the power supply has a series of outputs 16 to which thevarious consumers are connected. In the embodiment as shown in FIG. 1all outputs 16, except for the output provided for the starter, aresafeguarded by an upstream fuse. The output identified 16 a is providedfor connecting the vehicle lighting, primarily comprising incandescentbulbs. Included upstream of this output 16 a is a semiconductor switch18. This semiconductor switch 18 is driven by means of a driver circuit20 from a digital controller 22. By pulse width modulating the output 16a an operating voltage is furnished whose rms value is limited to theoperating voltage of the incandescent bulbs used in the vehicle lightingsystem.

[0013] Upstream of the group of outputs identified 16 b in FIG. 1 asemiconductor switch 24 is inserted. This semiconductor switch 24 isdriven by a driver circuit 26 controlled by the digital controller 22.Since the starter is connected to one of the outputs, 16 b, thesemiconductor switch 24 is provided with a very low impedance byconnecting several semiconductor elements in parallel, an impedance ofless than 0.5 mΩ being achievable at 25° C. by connecting eight MOSFETtype semiconductor switches in parallel.

[0014] At the input end the driver circuit 22 has a plurality ofinterfaces for connecting analog and digital signals representing thevarious operating parameters, also belonging thereto being an interface30 for connecting a bidirectional bus system (CAN).

[0015] In optimizing the charging voltage two variables need to betaking into account, namely the internal temperature of the rechargeablebattery and its charge condition, the temperature on the rechargeablebattery directly adjacent to the positive terminal being adequatelyrepresentative of the internal temperature. In the power supply inaccordance with the invention a temperature sensor 32 in the form of anNTC resistor is arranged directly adjacent to the positive terminal ofthe rechargeable battery and connected to an A/D input of the drivercircuit 22. The charge condition of the rechargeable battery is sensedby permanently monitoring the charging/discharging currents andintegrating the values sensed. Sensing is done preferably in twosuccessive ranges covering a total range of 0.1 A to 800 A (80 dB). Forthis purpose two sensing loops 34, 36 are provided on whichmagnetoresistive elements are arranged as shown in FIG. 2.

[0016] Referring now to FIG. 3 there is illustrated the preferredembodiment employed for current sensing in a diagnostic application byplotting the starter current as an example.

[0017] Referring now to FIG. 4 there is illustrated how the chargecondition is optimized without needing to take into account thelimitations imposed by the incandescent bulbs of the vehicle lightingsystem or the like.

[0018] Referring now to FIG. 5 there is illustrated as a further exampleof the function achieved by the power supply in accordance with theinvention in diagnosing the condition of the alternator by plotting thealternator current in which the periodic voltage drops sigify defectiverectifier diodes.

[0019] The performance features made available by the power supply inaccordance with the invention can be classified in four groups:

[0020] 1. Battery management

[0021] charge condition by current integration

[0022] optional indication of charge condition

[0023] optimized charging voltage (temperature, charge condition, usefullife)

[0024] voltage regulation for all incandescent bulbs, preferably bypulse width modulation at approx. 90 Hz.

[0025] This first group of performance features ensures reliable batterycharging in all temperature ranges. More particularly the standby chargelevel can be increased for low temperatures, ultimately achieving longerlife for both the incandescent bulbs of the vehicle lighting and therechargeable battery itself.

[0026] 2. Consumers management

[0027] reducing consumption with priority control on the basis ofoperating parameters polled via a bus system (CAN)

[0028] two output modes: ignition ON and ignition OFF

[0029] adapting idling speed (fallup at low charge condition)

[0030] limiting starter active time (preventing misuse)

[0031] These performance features enhance the available standby chargelevels.

[0032] 3. Safety functions

[0033] short-circuit protection for starter

[0034] power OFF in an emergency (crash situation)

[0035] power OFF when intruder alarm system activated

[0036] power OFF during transport

[0037] These performance features enhance safety and security.

[0038] 4. Diagnostic functions

[0039] starter blocked, pinion not engaged

[0040] alternator regulator, diode defect

[0041] leakage currents

[0042] This group of performance features provides an optimum tool forchecking the vehicle electrics system.

1. An automotive electric power supply including a rechargeable battery and a distributor comprising an input for one of two battery terminals and a plurality of outputs furnishing a battery voltage for a plurality of consumers, wherein a semiconductor switch is arranged between an input for said one battery terminal and at least one of said outputs and is driven by an electronic controller, said controller having an input interface for sensor signals representing operating parameters.
 2. The power supply as set forth in claim 1 , wherein one of said outputs is pulse width modulated for driving the semiconductor switch.
 3. The power supply as set forth in claim 1 , wherein the pulse width modulated output is regulated to a maximum rms voltage.
 4. The power supply as set forth in claim 3 , wherein a charging voltage for the rechargeable battery is adjusted by a charge controller to a value optimized for criteria such as standby change level, operating temperature, charging condition and life, but irrespective of the withstand voltage of one or more consumers connected to the pulse width modulated output.
 5. The power supply as set forth in claim 2 , wherein incandescent bulbs of a vehicle lighting system are connected to the pulse width modulation output.
 6. The power supply as set forth in claim 5 , wherein the pulse width modulation has a frequency exceeding 50 Hz, preferably in the range of 90 Hz.
 7. The power supply as set forth in claim 1 , wherein by permanently sensing the consumer and charging currents and integrating current values sensed a characteristic indicating a charge state is generated.
 8. The power supply as set forth in claim 7 , wherein current sensing is done directly following said battery terminal in a plurality of adjacent current ranges.
 9. The power supply as set forth in claim 7 , wherein sensing the current is done by means of magnetoresistive elements.
 10. The power supply as set forth in claim 1 , wherein a sensed consumer current is analyzed for the purpose of diagnosing a condition of the respective consumer.
 11. The power supply as set forth in claim 10 , wherein from a starter current diagnostic information as to at least one of the following conditions is derived: starting engine firing pinion not engaged blocking.
 12. The power supply as set forth in claim 7 , wherein the sensed charge state is analyzed for the purpose of diagnosing a condition of the alternator.
 13. The power supply as set forth in claim 12 , wherein from periodic voltage drops in the charging voltage an indication is derived as to a defective rectifier diode of the alternator.
 14. The power supply as set forth in claim 7 , comprising a means for indicating a charge condition of the rechargeable battery.
 15. The power supply as set forth in claim 7 , comprising a means for detecting leakage currents.
 16. The power supply as set forth in claim 1 , wherein a temperature sensor connected to an A/D input of the controller is provided adjacent a positive terminal of the rechargeable battery.
 17. The power supply as set forth in claim 1 , wherein a bidirectional bus system (CAN) is connectable to the input interface.
 18. The power supply as set forth in claim 1 , comprising power OFF means in an emergency.
 19. The power supply as set forth in claim 1 , comprising power OFF means on intruder alarm.
 20. The power supply as set forth in claim 1 , comprising power OFF means for safe transport.
 21. The power supply as set forth in claim 1 , wherein a selective reduction in consumer current of at least one current consumer is controlled by the controller as a function of operating parameters.
 22. The power supply as set forth in claim 21 , wherein one of the operating parameters taken into account is the condition of the ignition switch.
 23. The power supply as set forth in claim 7 , wherein when the charge condition is low the idling speed of the internal combustion engine driving the alternator and the vehicle is raised.
 24. The power supply as set forth in claim 7 , wherein an ON duration of the starter is limited as controlled by the controller. 